A conventional semiconductor inspection apparatus supports a 100 nm design rule and technologies. Samples as inspection objects are wafers, exposure masks, EUV masks, NIL (nanoimprint lithography) masks, and substrates; the samples have thus been varying. At present, apparatuses and technologies that support a design rule for samples with 5 to 30 nm are required. That is, it is required to support L/S (line/space) or hp (half pitch) nodes of 5 to 30 nm in a pattern. In the case where an inspection apparatus inspects such samples, it is required to achieve a high resolution.
Here, “samples” are exposure masks, EUV masks, nanoimprint mask (and templates), semiconductor wafers, substrates for optical elements, substrates for optical circuits and the like. The samples include samples with patterns and samples without patterns. The samples with patterns include samples with asperities and samples without asperities. Patterns are formed of different materials on the samples without asperities. The samples without patterns include samples coated with an oxide film and samples with no oxide film.
Problems of the conventional inspection apparatuses are summarized as follows.
A first problem is insufficient resolution and throughput. In a conventional art of a mapping optical system, the pixel size is about 50 nm, and the aberration is about 200 nm. Achievement of further high resolution and improvement of the throughput require reduction in aberration, reduction in energy width of irradiation current, a small pixel size, and increase in current intensity.
A second problem is that, in the case of SEM inspection, the finer the structure to be inspected, the more serious the throughput problem is. This problem occurs because the resolution of an image is insufficient if a smaller pixel size is not used. These points are caused because the SEM forms an image and inspects defects on the basis of edge contrast. For instance, in the case of a pixel size of 5 nm and 200 MPPS, the throughput is approximately 6 hr/cm2. This example takes a time 20 to 50 times as long as the time of mapping projection. The time is unrealistic for inspection.
Such conventional inspections are disclosed in WO2002/001596, JP2007-48686A and JP1999(H11)-132975
However, in a conventional inspection apparatus, it is difficult to inspect irregularities in a surface of an inspection object with high contrast and also to detect very small foreign matters. Thus, it has been desired to further improve the technology for inspecting irregularities in a surface of an inspection object with high contrast.
It is desirable to provide an inspection apparatus capable of inspecting irregularities in a surface of an inspection object with high contrast.
One embodiment is an inspection apparatus including beam generation means that generates any of charged particles and electromagnetic waves as a beam, a primary optical system that irradiates an inspection object held in a working chamber with the beam, a secondary optical system that detects secondary charged particles occurring from the inspection object and an image processing system that forms an image on the basis of the detected secondary charged particles, in which irradiation energy of the beam is set in an energy region where mirror electrons are emitted as the secondary charged particles from the inspection object due to the beam irradiation, the secondary optical system includes a camera for detecting the secondary charged particles, a numerical aperture whose position is adjustable along an optical axis direction and a lens that forms an image of the secondary charged particles that have passed through the numerical aperture on an image surface of the camera, and in the image processing system, the image is formed under an aperture imaging condition where the position of the numerical aperture is located on an object surface to acquire an image.